Q: Are household ants, in large numbers, ever a health hazard? Can they contaminate food or otherwise spread germs?
A: They could be a hazard, at least in theory, since they can carry bacteria and might transfer them to food or an open wound. Various disease-causing organisms—including E. coli, Streptococcus, Shigella, Salmonella,and Staphylococcus—have been found on some species of ants, especially in developing countries. But there’s no evidence that this is a significant risk.
Regardless of the health issues, no one wants lots of ants crawling on their food and furnishings. Instead of using pesticide sprays, make your home less hospitable to ants:
- Store food in tight containers.
- Clean up any soiled dishware and food crumbs.
- Remove sources of moisture.
- Follow ants to entry points, and seal cracks and crevices.
- Wipe up invading ants with soapy water to erase their odor trails.
- Try ant traps.
If these measures don't suffice, you can dust boric acid (wearing a dust mask) or diatomaceous earth (silicon dioxide) into entry points, making sure to keep these substances out of the reach of children and pets.
Originally published October 2011; updated January 2019.